Here're the things I found disappointing about the A760, in no particular order. Some are fixed features of the phone itself, while others are software or format issues.
That 8MB memory limitation with no scope for upgrade is teh suck. I've managed to stay within the limit so far by ruthlessly deleting files on a regular basis, but I can see that a phone with just 8MB isn't a long-term solution for a (hehheh) power user like me. If you just need phone and PDA functionality, however, 8MB should serve you well enough.
Yup, that's right. The A760 comes with a WAP/WML browser, but there's no built-in HTML browser. I believe that the A760's souped-up cousin, the A768 does have one, but that's still a bit far away for me.
There seems to be only one HTML browser midlet available on the 'net, and that's proprietary. I downloaded the demo version to check it out, and it seems to work sort of OK except for some really stupid scrolling (no scroll bars). Since it's proprietary, you'll have to figure out the name yourself :)
As noted above, you can't use standard sync tools to synchronise the A760's address book, calendar, etc with Linux. I'm sure it will be available one of these days, so I'm keeping my fingers crossed and waiting.
In general, the A760 is reasonably fast. However, it does show appreciable delays in the following situations: