I just bought a Hamster Heaven for my new Syrian Buttercup after reading the reviews here. Thought I would give my input
Pros
-Spacious with a good tray depth for a decent amount of substrate and a selection of toys
-Sturdy - the base and cage sections clip on very firmly and the cage itself seems well constructed EXCEPT for one bar (see below)
-Deep enough that the two different levels don't make the cage seem crowded
-Large door is handy for getting Buttercup into her ball, she used to have to climb up to the door of her cage but now I can put the whole ball inside and she can climb in easily without me picking her up (we're not 100% cool with that yet!)
-The tubes are a good addition for hamsters who enjoy them but it's also great that they can be removed without compromising the overall cage function, same with the penthouse
-The selection of "extras" that come with the cage are good quality, the toilet is handy (if the little miss figures it out) and the water bottle works well
-The wheel is good and it's an 8 inch instead of the 6.5 inch you normally see provided with cages. It's not silent but with a little lubrication it isn't very noisy and will do until I find a decent price on a Wodent Wheel.
Cons
-The cage was tricky enough to put together, I read some Amazon reviews saying things like "how am I supposed to do this? I'm not an engineer!" And laughed because I am actually an engineer and so is my bf but we did take about 20 minutes to sort it all out (and cook dinner at the same time. Dinner suffered). The instructions on the website aren't actually that helpful, we mostly used the picture. The most awkward thing was how hard it is to get the tubes together, the cage being so large makes it hard to manoeuvre.
-The "ladders" are more like slides. Buttercup can't get a grip on them at all and doesn't use either of them. We put one of her old Ferplast tubes through the hole in the taller platform for her but she prefers to climb the bars up instead. I'm getting some bendy bridges to use instead.
-I would have preferred the green shelf to be solid. The design looks interesting but there isn't that much useable space on it
-The sunken food bowls are good for not tipping over but Buttercup preferred her old larger dish she could sit in to eat so I'm not using those either.
-The gap between the platforms is too large for her to stretch over but small enough that she thinks she can which has resulted in a few tumbles, it would be good to include some way of bridging that gap, I see a lot of people have made their own. I'm going to use a suspended ladder when it comes in the post.
-The right angles in the tubing are a bit difficult for her to manage, she's not very large for a Syrian and used the curved Ferplast tubes no problem but she doesn't really like the 90degree-vertical-90degree set up. I might remove them as she doesn't seem to really enjoy them and I'm having visions of her getting stuck
-One of the bars on the top penthouse door detached on one side with very little pressure. It's one of the top ones which is covered by the penthouse so it's not a huge issue but I did have to go around the rest of the cage checking there were no more bars that were going to come loose as she is a bar chewer sometimes.
Overall I'm pleased with the cage, the size more than makes up for the nitpicky things I've found and I got it for £59.99 from Amazon which is more than reasonable.
Hope this is helpful for someone
here's some terrible phone pictures!
Buttercup - Imgur
Re: Hamster Heaven cage review
Really detailed. I love that cage but I cannot get it here in the States. So, I guess I'll keep my tank setups. 
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