I just got an iPad 3 a week ago, and am still deciding whether I’m going to keep it or return it, so I’ll give you my impressions on it so far.
The lack of Flash has so far not been an issue with me, even though I initially thought it might be. For a long time I heard that was a big downside to the Apple stuff, but either because I don’t go to a lot of flash-required websites or because most websites now have alternate options for iPads, I haven’t run into any issues on that front. After reading a letter by Steve Jobs from a couple years ago explaining the decision not to support flash, I even understand the decision.
On the other hand, the decision not to have an SD card slot, and even when you get the SD card adapter, intentionally have a set of unnecessary restrictions with no apparent reason to prohibit external storage is a bigger issue for me. If I decide to keep it, I will probably be jailbreaking it in order to allow for using SD cards as external storage. I also feel that this is a blatant money-grubbing move by Apple to try to force people to buy higher capacity versions.
I’m very satisfied with its performance, as all the apps seem to function quickly and efficiently. This is sadly not something I can say for the several Android devices I have had or tried in stores - sometimes even display Android tablets in stores have major hiccups and delays. As much as I prefer the fact that Android devices allow you to do more of whatever you want with them than Apple devices, the fact that my iPad has so far never frozen or made me wait for a minute before it would respond and so on is a big plus for it.
For web browsing, the iPad works fine. The onscreen keyboard also works far better than I expected it to, and I can type at nearly full speed on it - it’s big enough to make it possible to touch-type, and sensitive enough for that as well. I don’t have much experience in photography so I couldn’t tell you what it can or cannot do for you on that angle.
The ‘G thing’ I believe you’re referring to is wireless connectivity through cellular radio. I can’t speak to its usefulness because I thought the expense was too much for what I was getting - neither of the available wireless plans has unlimited data transfer, and the monthly cost felt high (capping out at 5GB/month for $50). 3G/4G is simply the difference in bandwidth you get.
Overall, I would suggest going to an Apple store if one is in your area and taking a look at the iPads yourself. The staff at the one in my area was reasonably helpful and knowledgeable, suggesting various apps to do what I wanted out of it. Being able to try out the basic functions on their demo models was a big part of selling me on it, as well as exposing the concerns I have so far that I’m yet undecided on. I’d also look into the details of jailbreaking the iPad and ask yourself whether you’re going to need to do it to obtain the full functionality you desire, and whether you’re willing to do it.
If you don’t like the Apple offerings, one thing to consider (if you are not in a rush to get your tablet) is that Windows 8 is scheduled to release in October, and several companies are intending to release tablets to coincide with it. On the other hand…first generation.