I don't think it would hurt you to swap your 1G to the 2G, provided that you were planning on upgrading to the 2.2 software (and paying $10 for it) anytime soon so that you can get applications. If you weren't, then sticking with the 1G is fine. I actually did pay for the upgraded software for my 1G.
The speaker on the 2G isn't all that great. It is much louder on the iPhone. I've also heard louder on other players that have built-in speakers. For me, however, it is a non-issue as a carry a small portable speaker with me (Altec Lansing Orbit). I do like the addition of Nike+. I use it when my Garmin Forerunner can't pick up a satellite. It's not as accurate as a GPS, but you can calibrate it so that it comes pretty close.
If you're going to get docking type accessories for it that use the proprietary port (the 30 pin dock connector), make sure that it specifically works for the 2G. Older accessories should work, but you'll possibly lose charging capability. For example I have a home clock radio and an fm transmitter dock for my car. They both work for the 1G Touch, with full functionality - plays and charges. However, they only work for playing the 2G. They won't charge it.