I used a DSE701 for a while, and while it was a step up from the mini I started with, it just wasn't that good compared to the eGo I got later. The 701 vapor is cold and unsatisfying, and I prefer the ease of use of 510-style cartomizers. Also the 701 has a cheap plasticky look and feel to it.
If somebody ever makes a quality cigar that uses oversize cartomizers and gives the same kind of vapor, but at higher volume than a 510, I would be all over it.
PS I also tried the 601 which was a completely dismal product. I posted a brief writeup in the review forum. It is made by the same manufacturer as the 701 and they are of similar cheap build quality.