Price Paid:  $200.00 from Craigslist Chicago

Summary:
Nice speakers with a bright character. In that sense its strengths are also its weaknesses... they're sharp, detailed, clear and dry. If you like that kind of sound, the NHT 1.8 are totally great. If you're looking for a warmer room-filling sound, this is not what you want. For $200 used, it was a total steal.

Weaknesses:
The sweet spot is small. The bass is tubby around the 100hz area, but you shouldn't expect miracles from 5' woofers to begin with. The tubby bass either has to be EQ'ed down and/or paired up with a subwoofer to cover the lower end of the bass if you want to balance things. Adding a subwoofer actually does miracles to the NHT 1.8, as it serves to make its dry character more warm and colorful.

Price Paid:  $400.00 from Local shop

Summary:
I replaced the tweeters with the soft dome version used in newer NHT models like the Superzero, Superone, etc. Together with that I redesigned the high pass filter for it using high quality parts. This is a long and painful process. I also changed the internal wiring to OFC wire. They now sound AMAZING.

Please see more detail below.

NHT speakers are highly recommended. I have no idea about the new Revolution series though.

If you can find the 2.1 or 2.3a used, they are better and already have the soft dome tweeters. These are very good tweeters too. Newer models are unlikely to be better except for the 2.9 and 3.3. The 1.8, 2.1 and 2.3 all have their dual woofers in sealed cabinet. NHT officially say that woofers in sealed box sound better.

Strengths:
Great bass response. Superb imaging and dynamic. Good looking too.

Weaknesses:
Upper midrange was a bit thin before I replaced the tweeter.
Small sweet spot.

Similar Products Used:
Only bookshelf, this is my first floor standing speakers

Summary:
I picked a pair of these used for $400, and I am very impressed.I have listened to many speakers and like the NHT line a lot (their
sound is not for everybody, but I like them). I narrowed down my
search to the 2.5i and waited to save the $1400 for them (spend the
extra $$$ for the mahogany finish: simply beautiful)

The 1.8's are 95% of what the 2.5's are, sound-wise, so I couldn't
beat the price. The base on them seems a bit deeper, but not quite as
articulated as the 2.5s. Mids and highs seem about the same, as is
the soundstage. I later talked to the man I bought the speakers from
who sold them to "upgrade" to speakers in the $1500 range: after
looking around a lot he was really bummed out that sold them to me!

I give these speakers 5 stars for the support I got from NHT. When
I bought the speakers they had no spike kit, and the crossover on
the left speaker died (not sure whether this was my fault or not).

I got great help from NHT for both of these issues, and my speakers
are working great now.