I’ve heard good things about this series, and of course the SDMB is full of tasteful people. 
Here’s what I like already (and how much):
West Wing 10/10
CSI (Vegas) 10/10
CSI (Miami) 8/10
CSI (NY) 6/10
Law + Order (original) 10/10
Law + Order (Criminal Intent) 9/10
Law + Order (Special Victims) 7/10
Murder One 9/10
OK - over to you!
Boston Legal isn’t like any of those shows. The shows you listed are serious dramas. Boston Legal keeps its tongue firmly in its cheek. It’s more satire than straight-up legal drama.
It’s hard to compare the show to others, since it’s fairly unique. Just rent the season 1 box set and watch the first few episodes. If you don’t like it, you’ll know by then.
You seem to like serious police dramas. Boston Legal is a dramedy so the shows you list do not make for a good comparison.
Did you like Ally McBeal? This show has a similar feel to it. It is a not serious lawyer show. The acting is a little over the top, but if you like CSI Miami, no worries there. 
It is quite funny, fairly entertaining and employs a large mix of Hollywood Veterans and newcomers. I like it; I just do not remember to watch it when it is on. I have missed far more shows than I have seen, and it does not seem to affect my enjoyment of the show despite some ongoing plotlines, I am clueless about.
Shatner is in the role of his life, as he appears to be largely playing himself or at least the caricature of himself.
Jim
If you like the serious stuff, then maybe BL isn’t up your street because it’s packed full of satire. James Spader is just so funny, although I did get a bit confused when he popped up in “The Practice”.
Give it a go anyway, you might be pleasantly surprised. I didn’t think BL would appeal to me based solely on my experience of William Shatner’s character, but after a couple of episodes, it grew on me.
Thanks for the comments - much appreciated. 
OK, so Boston Legal is more like Ally McBeal?
I thought that show had its moments (and certainly had a consistent style).
Plus it had Lucy Liu (sorry, personal moment there 
).
How does Boston compare to LA Law?
I can’t comment, I’ve never watched Ally McBeal or LA Law. All I can say is that BL is very tongue-in-cheek and satirises the legal profession very well. The characters are great, it’s very well scripted, and James Spader knocks the socks off the rest of the cast.
Give it a try and see what you think - it defiinitely grew on me, and I’m very hard to please! You may be disappointed by the lack of emaciated airheads though…
I don’t remember a lot of humor in L.A. Law. Except for maybe when Diana Muldaur – no, bad AuntiePam.
If you’re nitpicky about procedural stuff, Boston Legal will take some getting used to. They’ll get a case and go to trial in the same episode, for example. The lawyers (especially Alan Shore) do things that would probably get them disbarred in real life.
Great show. Lots of genuine feeling, a bit preachy, but thoughtfully done.
I’ll just echo what most of the other people here are saying. The shows you mentioned, with the exception of the West Wing (which is in a class all of its own), are all sort of “formula shows” - CSI, Law and Order, wherever, whatever, they all follow pretty much the same formula in every episode, and even the roles on the characters within the shows are similar. If you like serious solve the crime/put the guy in jail crime dramas, you know what you’re going to get with a CSI or L&O.
Boston Legal tends to have a lot more fun playing around with things, doing them in different ways, and just generally being satirical and funny in addition to the drama that it keeps there to hold everything together. Like AuntiePam said, it can be a bit preachy at times, but it doesn’t usually end up taking too much away from the show.
I’ve also never seen Ally McBeal or L.A. Law… but David E. Kelley was heavily involved with L.A. Law, was the creator/head writer for Ally McBeal, and is the guy behind most of Boston Legal (along with quite a few other things, too - check out his IMDB page if you’re curious). So I’d think it’d definitely be more similar to those, if only in style.
“Boston Legal” has a lot more wacky, offbeat stuff than “LA Law” typically had. In “Boston Legal,” even the scenes in the courtroom are often puncuated by nutty characters saying and doing weird things. Some of the nutty characters are series regulars: William Shatner, for example, seldom has a scene that is played straight.
In some ways, “Boston Legal” reminds me of some of the '80s sitcoms with large ensemble casts. “WKRP” and “Taxi” and “Cheers” come to mind. It is as if the freewheeling spirit of those shows has been grafted onto a legal drama.