Pros: Solid, reliable Marine and Amateur Band HF SSB
Cons: Unwieldy frequency selection process for Amateur Frequencies
We have used our Icom M710 (we have the RT model with the remote head - it has the same features, functions and electronics as the base model) for 8 years and the unit has proven to be the most reliable Marine SSB model in the cruising fleet.
We use our M710 daily for Marine Voice Radio networks on Marine and Amateur Radio Single Sideband (SSB) frequencies and she has never let us down. The reciever selectivity and sensitivity are supurb. The transmit power is as rated, the audio quality is great and the tuner matches our insulated backstay antenna perfectly. With our bonded ground and foil ground plane we have one of the strongest signals in the fleet.
We also use our M710 with a SCS PTCII Pro packet radio modem with Winlink (http://winlink.org) and Sailmail (http://sailmail.com) for email at sea. We highly recommend this configuration as it has also served us well for years.
As with any SSB radio, proper training is required for the operator. A marine station license and operator permit is required for marine use (no tests, just a filing fee with the FCC for US residents) and an amateur radio General or Extra class license is required to operate on ham frequencies (see http://arrl.org for more information on obtaining your amateur radio license).
Unlike Icom's new M802 model, the M710 has not had any systemic techical problems. The M802 had a problem in certain installations that resulted in clipped audio on transmit. See Icom Knowledge base article: http://www.icomamerica.com/en/support/kb/Article.aspx?ArticleNumber=732B232987 for details.
The only downside to the M710 is the somewhat user hostile transmit/receive frequency selection process for amateur radio frequencies. Fortunately there is a firmware modification available to make the radio "Ham Friendly" from dealers like Don Melcher at HF Radio in Alameda California see http://hfradio.com/Information/ssbham.html for more information.
If you are in the market for an M710, please make sure that the radio you buy has been opened up to the amateur radio frequencies if you have a ham license. Also make sure you get the US and not the European model as the EU model does not have the freedom to reprogram the channels that the US model does.
A reliable dealer will help you enormously in this regard and with the radio's installation as it can be quite complex.