Fine with me. I used to love him when I was in my teens but after volume 12 or so of the Discworld series (Lords & Ladies?) I just couldn't go on. I picked up another one of his a year or so ago - Thief of Time - just to see if I was missing anything, and I found that all the old weaknesses were there in spades:
1. He inhabits a place where the only dramatic engine for a story is the threat of the end of the world - in that case by time being frozen. Even though you know it'll all be all right in the end, however suddenly and ridiculously (see 3 and 4). While it makes a change to read a book with an actual, factual baddie in it, the problem is that when the end-of-the-world schtick is all you've got, it becomes necessarily inconsequential. And then we're in trouble. (Hey! A plot for the next book!)
2. Although there are several excellent jokes in Thief of Time (many in the footnotes - Pratchett has long used these to replicate in prose the expert timing of a great stand-up comedian: not a bad trick), boy does he know how to trample the life out of a running joke! The abbot, for example, who inhabits the body of an infant and interjects his statements with "BIKKIT!" and "wannapottynow!" All the time. For two hundred pages. Hilarious.
3. It's full of the pretentious horseshit I remember that I used to hate even when I liked him. All that prosaic poetry and magicky crap like "It came from the darkness ahead, a slow beat that was ridiculously familiar, a heartbeat magnified a million times, each beat slower than mountains and bigger than worlds, dark and blood red." Usually this doesn't turn up until about 90% of the way through the book (see 4), but here it kicked in before page 50.
4. I could tell early on that it was going to fit the usual pattern of Pratchett plotting, what Martin Amis denounced as the habit of popular fiction where the last 90% of the action takes place in the last 10% of the book. In Pratchett this sin is usually compounded by the resolution being brought about by nebulous magicky horseshit (see 3). This was evident even halfway through Thief of Time (where I gave up) where nothing had happened yet apart from a whole load of scene setting (see 5).
5. A whole load of scene setting; dozens of pages in a row of top-heavy conversations full of explication and backstory. Worse are Pratchett's creaking attempts to make things new while keeping it consistent with what happened in the previous 25 Discworld novels ("I thought you could remember the future!" "Yes. But something has changed.").
So for these reasons and more (when I can remember them), I just let Thief of Time slip quietly away. For is it not written that, in the grand tradition of Lennon & McCartney, Morecambe & Wise and ... er, Les Dennis & Dustin Gee, similarly when it comes to the pairing of Douglas Adams & Terry Pratchett - truly the wrong one died first. No offence like Terry mate!