post some work photos so we can see whether a PR firm could help you or not... what's your market?

Maybe? 

Yes, I've used similar; I hired a publisher. It isn't so much gaining clients directly from things getting published (like getting cold called after someone reads it), it is used more so to establish yourself in the market so when a prospective client is deciding between you and a competitor, publications help establish you as 'the firm' making headlines others in their industry look to.  Look for someone familiar with the market you are looking at.  Like I did fire stations, and they have their own publications and websites they regularly go to for just industry happenings (sort of like our architecture magazines written for architects). I'd put out articles for new directions and thoughts on advances in firehouse design. Most often, the technical sort of articles worked best for publications and would get published. Rarely did those publications want a full station review, but were always interested in design considerations and new trends. Again though, it is about establishing your firm as 'the experts'; plenty of others may have the experience, but you are the one their publications go to for articles, advice, etc. rather than your competitor.

It worked better than a strict outside marketing firm who just looked for clients and often sent me shit leads everyone else was also pursuing.  

This maybe of interest?

That approach seems very random, with the end result being that hopefully, hopefully someone sees it and colds you ( not likely a real project and chances are really low that it translates into a proper project ), your ego will be happy because you are published, the cost will be significant. 

I would suggest something more targeted and strategic that has a better chance of being translated into a real project, IE work with local contractors, real estate agents, developers etc. 

Assuming your work has the right "look" that publications are seeking, investing in PR services is perhaps worth it on one condition.  It is worth it if you can be certain that the PR person has relationships with elite publications that you could not form on your own.  

The fame-chasing architects I have worked with did 95-100% of PR with in-house marketing staff.  The firm principals would suck up to magazine editors by attending events where they knew they would be.  People also use certain big-name design photographers who have relationships with magazines and book publishers.

The real trick my old bosses never learned is to get published where monied clients will see you rather than being in things read just by other architects.  Think RobbReport or Business Week instead of Architectural Record.  Some magazines walk a line between both crowds, like Dwell.

 Some of my friends who are in larger firms use them. Im not sure if they find it worth while or not.

FWIW, we have never found it hard to be published, especially online and often have companies contact us for material for books and online this and that. For that kind of service to be worthwhile for us would mean to get us published in places outside of architectural press and for those publications to NOT be the kinds of place that routinely ask us to advertise by paying for an article to be included in their publication. There are a lot of scams like that out there and having someone who can navigate the bullshit in a meaningful way that actually leads to recognition would be great.

My honest opinion on that front is that it is not so easy to do the job properly and that mere  publications and online hits is not a meaningful measurement of anything. If working with someone be sure to set your goals and what you expect the metric to be. That should clarify what they are able to do and what value it will have.