Hi. For what it is worth I am a owner of a Extrawheel Voyager so here is my five cents worth. Oh BTW I had a
BOB Ibex before this .... First up I haven't had the handling issues that others have mentioned and I have used both trailers on the bitumen roads, down hills at speeds around 50 km/h, on gravel forestry roads and on single track (mountain bike trails). I have also and do tour with just panniers. I make my decision as to which way I go depending on the tour. My
review of the Extrawheel Voyager can be found here. I am heading off in July on a 5,000 km ride and yep it is coming with me.
BOB Ibex in action on the
Munda Biddi Trail in 2008:
As a side note, Perry who was riding with panniers on this ride went out when he got home and brought a BOB Ibex after seeing mine in action on this ride.
The Extrawheel Voyager on it is
shakedown tour. Again this included some of the Munda Biddi Trail but this time riding my
Surly Long Haul Trucker. Not the best choice for the Munda Biddi Trail but
Back to your questions.
How does the bike handle with one of these in tow?
In my experience so far it handles fine. I really don't notice any handling change and as I said my biggest issue on the single track was not the Extrawheel Voyager, it was the Surly Long Haul Trucker. All my focus was on the bike, the trailer got forgotten about. I find that other than really tight spots I forget about the trailer.
Going down hill I have descended both bitumen hills and pea gravel hills. On the bitumen I hit around 50 km/h and found that was okay but I wouldn't want to go much faster than that. On the pea gravel I maxed out at around 20 km/h because it hurts when the front wheel washes out

I have ridden pea gravel a lot without a trailer and didn't notice any significant difference in the riding experience. It is a pain either way.
Is it as light and unobtrusive as they claim?
Light? It weighs 4.1 kg by my scales (sans panniers) so I guess you need to decide if that is light or not. It is lighter than the BOB but of course it adds weight to the bike overall. Unobtrusive? I guess you have to make that judgement. I switched to the Extrawheel Voyager for a couple of reasons, one of which was to be able fly more easily with a trailer than I could with a BOB. I am expecting to pack the Extrawheel Voyager into the same bike box as the Surly.
Is it really a better option than cramming all the weight over the back wheel on the bike?
I would say yes in that any re-distribution of the weight is better. Is it better than using front and rear panniers? From my experience I wouldn't get one just to do this. As I have said I have toured with both the Extrawheel Voyager/BOB Ibex and with panniers only and I make the choice based on my tour. What is my preference? Extrawheel Voyager but I really cannot put my finger on why that it is my preference. There is simply something nice about the overall experience/feel of the bike that I prefer but it is not a deal breaker for me in terms of which way I choose to go. I also go with a trailer for two reasons: (1) I like to tour with my mountain bike and I don't want racks on it if I can avoid them and (2) because on some of my tours I simply need the extra load carrying capacity.
What is the build quality like?
Looks very good to me. Nothing has jumped out at me so far. It was easy to assemble and from what I have seen of in use on some serious rides it has survived okay. I have yet to put more kilometres into to judge durability. That said I am trusting it on a 5,000 km tour on some pretty rough rides. I hope it stands up to it!
Closing Comments
If I was in your situation and didn't want to put a rack on the front then I wouldn't have an issue using the Extrawheel Voyager based on
my experience with it and with the BOB. I would choose it over the BOB but. That all said if I was flying off to the UK to tour or to Europe I would probably fly with my Surly and panniers, but then my Surly has front racks

Equally it wouldn't bother me to go with the Extrawheel Voyager.
Hope that helps
Andrew