Not a flawless show, certainly, but its great moments were amazing. It has to be watched in context: for an early 90's network TV show, WOW. but compared to a modern, high-profile show produced by HBO or AMC, well,... OK, it might not be quite as riveting. I really enjoy it, but I must admit it isn't as consistently good as say Rome, which has outstanding writing through and through. However, at Twin Peak's best moments, it is as good as television gets, at least for me. Give it a chance, and if you do, try not to read anything about it before you watch it. It is best seen with surprises intact.
Another superb classic TV show I will mention is I, Claudius, if you haven't seen it. Fantastic writing and characterization, and amazing cast. If you can get past the stagy BBC production techniques of the late 70's, easily one of the best shows ever produced, and not matched until Twin Peaks, in my opinion.