Well, it's not as posh, but I don't have to keep to any special coffee thingies. You buy coffee pods for it, but I bought some reusable ones, so I can use normal ground coffee (or grind my own). Works out cheaper. I use it twice a day and have done for about 4 years, so it's worn well
It really does depend on what you are looking for. My friend likes the chocolate from the tassimo. You can't do that with the Senseo. Actually...perhaps you can...not checked, but it's not marketed as such.
I had a Tassimo for a couple of years and really liked it. Used it to death tho and when it gave up the ghost a few weeks ago I replaced it with a Dolce Gusto, which think is really good. The plus points of the Tassimo have to be the variety of drinks you can get, the downside for me was that you can muck it up by not getting the pod in correct and then you get granules all over the machine which takes ages to clean up. I think the pods are easier to use in the DG.
Both are good machines, I prefer the DG now I've got one, but would still happily recommend the Tassimo.