Sure its still very good. The occasional great line, great acting and scripting, and well realised characters.
Buuuu-uttttt!!!! - it's efforts to keep its finger on the pulse of modern English politics is, paradoxically, making it increasingly irrelevant. The first series satirised not just "New Labour", but NLs emphasis on media manipulation, and specifically Alistair Campbell's (by the time of the first series...) famously bullying take on "spin". This was particularly ripe for satire, despite the fact that AC was (as I've mentioned before) gone for a couple of years by the time the show came out.
The new series falters, even though the emphasis, the main "comedy moments", remains about party political spin. This is possibly because it is too modern - current politics don't have any party with the confidence and power to attempt the "malcolm tucker/alistair campbell" style of political communication. The "new agey" style of Stewart from the tories simply does not have the same comic potential as Tucker in his prime. Similarly, Tucker in opposition feels like a ghost of the past; a character brought back mostly to keep the fans happy. AC is, in reality, a highly sought after guest speaker, earning almost as much as Blair, and would be highly unlikely to come back and help labour move out of opposition. The LDs have been focussed on little thus far, but the biggest comic potential lies there.
The point being, though, that despite the attempt to focus on politics as it has been in the past two years, the last two years of politics are not nearly as well defined to most viewers, as the previous 8 were when the first series came out. I have no doubt that it is a brilliantly researched show, and I suspect that in "westminster circles" it will be considered the best series yet, but it is nowhere near as refreshingly original as it was when it started.
Still 10x better than almost everything else on telly, though.