I have several gripes, but they are all minor, and probably won't affect my next purchase. I'll be looking at Ice Cream sandwich tablets in the spring, but at this point, I doubt I will be changing, because I have gotten locked into the ecosystem, love Apple support for their products, and have had great experience with Apple stuff.
1. The proprietary connector.
2. Lack of a file system, which leads to inability to upload files to sites (yes, I am aware of iCab Mobile, but it doesn't work on many sites).
3. Lack of a file system, which forces me to either replicate files in different apps, or rely on one app alone to do something like read a PDF. Bad for developers (who cannot share consumers, because they get locked into one app) and bad for me.
4. Crappy cameras. I use it as a "scanner" for receipts, handouts, etc., but the quality is often too low.
5. Lack of options. I HAVE to use Safari as default, even though it doesn't properly display web pages (encoding messes up for foreign languages). I HAVE to use the Mail program as a default, even though it is too basic to be of much use. I HAVE to have Newsstand and other Apple bloatware on my device, and in the case of Newsstand, can't even put it in a folder. I HAVE to be very careful every time I backup, because I don't want to erase old versions of apps that worked and replace them with broken ones (this is partly a developer problem, and partly a problem with Apple making it impossible to access older/alternative versions of an app).