Coworking
To expand on a comment made by @henning:
Have you considered a co-working space?
and to offer my experience in the hope it will help in your decision-making...
About 18 months ago the company I work for moved offices. Up to then, the commute (by train) was long but manageable. However, the new offices were too far to realistically commute to everyday. The company was very accommodating ("we don't want to lose you because of this move") and were quite happy for me to work from home most days.
Although I had worked the odd day from home in the past (for example if the trains were kaput), it was a case of laptop-on-the-dining-room-table... something that can work for a day or two, but not most days of most weeks. The conventional wisdom is, of course, that if you are going to work from home it needs to be in a dedicated space where you can go "from home to the office" at the start of the day, and "from office to home" at the end (I've even seen people say that while they may not wear "full business attire" while in their home-office, they consciously "dress for work" and "change into something casual" at the end of the day to reinforce the home/work split).
Unfortunately, I wasn't in a position to create such a dedicated space (it might have been a possibility, but other things fell through). Instead, I looked around for a "co-working" space. This Wikipedia page goes into more detail, but briefly: you rent your own desk-space, often in a shared office with other co-workers (from other companies, or working for themselves). The company that owns the office space typically provides certain levels of amenities and "office facilities" (some included in the price; some paid as you consume them). For this type of space, you can (generally) kit-out your desk as required – I'm a programmer, and have two monitors and a docking-station permanently on my desk: I just come in and plug-in the laptop.
The advantages are:
You're still in a "real" office environment (at least to some extent; the number of people around you and their composition tends to change much faster than in a company office, depending on how long those other people rent for) – a degree of "social interaction" is easier to achieve than being at home.
There is a clear distinction between being "at home" and "at work".
Depending on where you can find space, your commute-time can be drastically cut (maybe not as short as walking from bedroom to home-office, but mine went from the best (worst?) part of two hours each way to a 7-minute train ride and a walk across the town hall square!) Although I was "OK" with my previous commute (I'd adapted to it over the years), reclaiming all this time was a massive boost to my "work-life balance").
A VPN means I can work as effectively as being in the real office, and Skype makes interacting with colleagues almost as easy (although as other answers have touched on, it can be easier to fall "out of the loop" if you and your colleagues don't make a conscious effort not to let that happen).
The downsides:
There is a disconnect from actually being in the main office (again as mentioned in other answers: the overheard discussion to which you would have replied "I know the way to fix that..."; the social intercourse with colleagues is not the same).
There is a cost involved: as with "real" office space, this is going to vary by location. In my case, the monthly rental is near-enough the same as the cost of commuting to the new offices would have been (and slightly higher than the old commuting costs). For me, that slight increase is a small price to pay for the convenience of not having to commute every day.
Obviously everyone is different, but I can say co-working works very well for me, and should definitely be something to consider.