I purchased my Weber manifolds from Moss in the UK, and fabricated the linkage. I bought my Webers used and rebuilt them. I'm using twin 40DCOE's, but I have extensively upgraded the cylinder head (larger valves, ported and polished head, upgraded springs, fast road cam) to optimize their performance. I do NOT have any problems (no hesitation, no "typical" flat spot, etc) with them. The key is in the jetting. Unless you plan on significantly modifying the head, however, you will probably not realize the real value of the carb(s). The machine shop and parts charges for my cylinder head improvements were about $1700 in 2005.
Not knowing what your budget is, I can tell you personally that tuning Webers can be expensive, re the cost of "experimenting" with different jets, venturis, etc. to optimize the value of the carbs. Although the standard Weber carb set-up sold by many suppliers is usually a good baseline, getting to the problem-free point will most likely involve trying different combinations.
If you are working on a strict budget, I'd focus on modifying the cylinder head and consider upgrading to dual 1.5" SU carbs, a setup that was offered in England/Europe. Periodically, you'll find these used on eBay for a reasonable price. I love the look and sound of the Webers, but from what I hear the 1.5" SU setup is very good. Add a good quality tubular header and appropriately sized exhaust system, and I think you'll be pleasantly surprised.....