When you say you'll probably use the internet an hour a day or so, I think you will be surprised as a lot of apps you can get use real time (or close) data in the Iphone so you may find this sort of thing useful - its not just about browsing.
I had one but it wasn't for me because:
1. You can't transfer all contacts in a single action. This may not affect you as yours are already in the Lex system and I assume you would be transferring new or just deleting the odd ones. I work on different contracts for a couple of months at a time so will have a good 60+ phone numbers of the subbies, etc so transfer, remove and add knew ones with each project. Couldn't be done in a single pass with the Iphone. It could be an issue for you if ever they were cleared. As a one off, it would be worth fiddling around with a PC and another bluetooth device (like keeping your existing SE) in getting them back on. Doing it frequently is just a pain.
2. I wasn't impressed with the handset sound as a phone.
3. On the Lex, If I received a second call but can't take it, then get an answerphone txt, it would lockup the bluetooth and the phone would hang.
4. I use the cut and paste a lot and it is important to me. Possibly a utility for this now or even the latest software perhaps?
Some of these may have been addressed in the latest versions. If not, there may be hacks but I guess you wouldn't be doing that sort of thing so would lose out. There are other things that you may need applications for (like MMS) so it would be handy if you knew someone if you don't like to play at installing these things yourself.
No one can deny it is a great piece of kit but if possible, try and borrow one and test for yourself because, and I know someone will find this hard to accept, it may just not be right for you at the moment. Whether the Lex's fault or the Iphones fault - it still amounts to the same and worth thinking about.