I too am on Tysabri and am overall very happy with it so far.
I started it last November and unfortunately it can increase your risk of infections, which seems to be the case for me. I've been on antibiotics a few times. However, other patients I've talked to don't seem to be having this problem.
On the plus side, I feel WAY better since starting Tysabri. I have more energy, I think more clearly, and I feel stronger and a little less numb too! I just had my 6 month follow up MRI on Sunday, and find out in a couple weeks how my lesions are looking. I've heard many stories of lesions shrinking and things stabilizing. I hope that's true for me too, as I too was having many relapses. I was on Betaseron for a year and a half and it just wasn't good enough.
The decision to start Tysabri for me was an easy one, as I have no kids and was heading down a road my neurologist and I didn't like - lots of relapses and incomplete recoveries from them. The good news is, as far as I've heard, there have been no new cases of PML in the 2 years that Tysabri has been back on the market.
Good luck with your decision, if I can help please feel free to email me.
Diagnosed with MS April 2006
Started Tysabri Nov. 2007